Boring or drilling a hole accurately at a required angle or to a required depth using an electric hand drill typically requires some form of supplementary angle or depth-indicating device. Some devices, for example, air-bubble level indicators, are attached directly onto a drill. These have the disadvantage of being unstable and perpendicular to only one plane of the surface to be drilled. In order to achieve a true perpendicular angle with the surface to be drilled, both planes that form the right angle must be accounted for. The same is true for other angles.
Another type of angle-indicating attachment mounted onto an electric hand drill combines one or two shafts with springs. This device, of irregular shape and easily broken, is cumbersome to attach and use. After repeated use, the gap between the shaft and the shaft-slide holder tends to widen, causing the angle indicator to loosen and shake during drilling.
Some housing attachments have the disadvantage of the guide itself possibly slipping away from the surface and ceasing to function as a resisting force, as a stand or shaft-and-spring will do.
To gauge the depth of the hole to be drilled with accuracy, a resisting-force type device is preferred, especially when the work piece is made of softer materials, such as wood. In these instances, some devices cause a spiralling motion of drill bits, especially those of large diameters, which actually pulls the drill into the material. The operator of the drill thereby loses control of the push-and-pull tension with the material being drilled, which results in the drilling of a hole deeper than intended.
Adjustable-angle drill attachments are non-essential, yet they require a drill user's constant attention and are time-consuming to deal with. Most jobs that use an electric drill require only a few angles, the most common being ninety, sixty, and forty five degrees.